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  4. Dynamics of sedimento-lithogenesis and hydrocarbon generation in devonian sequence of the Lviv depression based on the results of geochemical and palynological studies

Dynamics of sedimento-lithogenesis and hydrocarbon generation in devonian sequence of the Lviv depression based on the results of geochemical and palynological studies

JGD.
2025;
Volume 2(39)2025, Number 2(39)
: 29-42
https://doi.org/10.23939/jgd2025.02.029
Received: June 18, 2025
Revised: October 09, 2025
Accepted: October 22, 2025
Authors:
  1. Natalia Radkovets
  2. Antonina Ivanina
  3. Yuriy Koltun
  4. Ihor Shaynoha
  5. Halyna Hotsanyuk
1
Institute of Geology and Geochemistry of Combustible Minerals of National Ukrainian Academy of Sciences
2
Ivan Franko National University of Lviv
3
Institute of Geology and Geochemistry of Combustible Minerals of National Ukrainian Academy of Sciences
4
Ivan Franko National University of Lviv
5
Ivan Franko National University of Lviv

The purpose of this work is to study depositional history and the dynamics of post-sedimentary transformations, in particular the thermal maturity of kerogen in the Middle-Upper Devonian rocks of the Lviv Paleozoic Depression. Methodology. This study utilized an integrated approach involving geochemical analyses, specifically focusing on parameters of Rock-Eval pyrolysis such as total organic carbon content, temperature Tmax, S2 oil potential, and palynological studies that included the color index of microfossils. Results. The results from the combined geochemical analysis (involving 20 core samples from 9 wells through Rock-Eval pyrolysis) and palynological analysis (44 core samples from 8 wells) allowed for determining the content, genetic type and generational properties of organic matter in the Middle and Upper Devonian rocks of the Lviv Paleozoic Depression. The rocks contain kerogen of both marine (type II) and terrestrial (type III) origin. Based on palynological studies, the kerogen was found to contain humic and sapropelic-liptinite components. The thermal maturity level of kerogen was determined using both Rock-Eval Tmax parameter and the color index of microfossils. Within the Lviv Paleozoic Depression, three zones are identified according to the degree of thermal maturity of kerogen. Originality. As a result of this study, the sedimentary and post-sedimentary evolution of the Middle-Upper Devonian strata of the Lviv Paleozoic Depression was investigated. For the strata of this age range, the combined use of palynological and geochemical methods has been applied for the first time. This made it possible to estimate the thermal maturity of kerogen in organic-rich rocks in different parts of the Depression. Practical significance. The comprehensive geochemical and palynological studies allowed to establish the regularities of the processes of thermal maturation and hydrocarbon generation in the Middle-Upper Devonian rocks of the Lviv Paleozoic Depression. Based on these findings, we can determine their potential role in the formation of oil and gas accumulations.

Lviv Depression
Devonian
kerogen type
temperature Tmax
color index of microfossils
hydrocarbon generation zones
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